A print data adaptation apparatus, such as a scanning device, such as a thermal printing device, such as a copying device and such as a facsimile device are known, namely from a facsimile apparatus which is commercially available from the Applicant under the type designation xe2x80x9cMagic Voxxe2x80x9d and which is a multi-purpose apparatus having a copy mode as well as other modes. In the copy mode of the multi-purpose apparatus the contents of a document can be copied onto a printable medium.
In the copy mode a scanner of the scanning device is activated, which scanner is adapted to scan the contents of the document in a dot-by-dot fashion and to generate and supply scan data in accordance with the contents of the document. The scanner has a scanning head having 1728 optical sensors. Each sensors has a scanning dot size of 0.125 mm corresponding to a diameter of the sensor. The sensors are arranged in rows, thus enabling the contents of a document to be scanned by means of the scanner in a dot-by-dot fashion along a row. Furthermore, in the copy mode a document feed roller forming part of document feed means is active and causes the document to be advanced stepwise by a scanning row feed which essentially corresponds to the scanning dot size. This makes it possible to scan the contents of the document in a dot-by-dot fashion along successive rows. On the basis of the construction of the scanning head and the construction of the document feed means a resolution in the feed direction of the document, i.e. a so-called vertical scan resolution, of 200 dpi and a resolution in a direction perpendicular to the feed direction of the document, i.e. a so-called horizontal scan resolution, of 200 dpi can be achieved during scanning. The scan data generated during scanning form a digital representation of brightness values of the document contents, the brightness values being quantified in 256 brightness levels.
Moreover, print data adaptation means are active in the copy mode of the multi-purpose apparatus. The scan data generated by the scanner are applied to the print data adaptation means via receiving means. Subsequently, the scan data are preprocessed in the receiving means so as to quantify the brightness values in 128 brightness levels. In the data conversion means the scan data are converted into print data which are printable by a thermal printer in accordance with first conversion information based on a conversion table. During the conversion the 128 brightness levels are converted into 64 gray tones, the digital representations of said gray tones forming the print data. The print data can be supplied via output means.
Moreover, a thermal printer of the thermal printing device is active in the copy mode of the facsimile apparatus, which printer is adapted to print print data onto a printing medium and which in the known multi-purpose apparatus effects printing on a printing medium with the aid of a thermal transfer printing process. For this purpose, the print data generated by the print data adaptation means are applied to the thermal printer. The thermal printer has a print head equipped with 1728 heating elements. Each heating element has a printing dot size of 0.125 mm, which corresponds to a diameter of the heating element. The heating elements are arranged in a row, as a result of which the thermal printer can print the contents of the document in a dot-by-dot fashion along one row on the printing medium. During a printing operation the printing medium is in close contact with a thermal transfer foil, as a result of which during heating of a heating element a heat-activated dye carried in the thermal transfer foil is transferred to the printing medium in a dot-by-dot fashion. This results in a dot-by-dot inking of the printing medium. A printing medium feed roller forming part of the printing medium feed means is also activated in the copy mode and causes a stepwise feed of the printing medium and a synchronous transport of the thermal transfer foil with a printing row feed which substantially corresponds to the printing dot size. On the basis of the construction of the thermal printer and the construction of the printing medium feed means it is possible to achieve a resolution in the feed direction of the printing medium, i.e. a so-called vertical print resolution, of 200 dpi and a resolution in a direction perpendicular to the feed direction of the printing medium, i.e. a so-called horizontal print resolution, of 200 dpi during printing.
In practice, a problem occurs in the known multi-purpose apparatus during copying of a continuous black area on a document, which area is large in comparison with the scanning dot feed and the printing dot feed. This problem is illustrated in the left-hand part of FIG. 2, which shows a detail at a suitably enlarged scale of a typical result E1 obtained when a continuous black area on a document is copied onto a printing medium. A plurality of dot-like black ink portions A1 printed on the printing medium are shown, which lie at the intersections of the printing row lines R1 to R5 with the printing column lines C1 to C5. As compared with one another, the individual ink portions exhibit a typical distinct anisotropy as regards their shapes, as is customary for a thermal printer. Furthermore, a plurality of blank portions B1 between the black ink portions A1 are visible, which blank portions have areas which vary in comparison with one another and which join one another in many cases. The discontinuous area on the copy, which area is formed by the black ink portions A1 and the blank portions B1 and deviates from a continuous black area, exhibits a residual gray tone which differs distinctly from black. The residual gray tone manifests itself in a reduction of a maximal image contrast, which in the present case means a reduction to less than 64 gray tones. This results in a substantially reduced reproducibility of details of the contents copied from a document onto a printing medium.
It is an object of the invention to solve the afore-mentioned problems with print data adaptation apparatus, with a scanning device, with a thermal printing device, with a facsimile, to provide an improved print data adaptation apparatus, and an improved scanning device, and an improved thermal printing device, and an improved copying device, and an improved facsimile device.
In print data adaptation apparatus this object is achieved in an advantageous manner such that the scan data generated by the scanning device and representing a continuous black area can be converted by the print data adaptation apparatus in accordance with the invention in such a manner that said print data can be printed by the thermal printing device operated in the second print mode and that during printing of said print data in accordance with the second print mode a substantially continuous black area is printed and the residual gray tone is largely avoided. This situation is illustrated in detail in the right-hand part of FIG. 2 at a suitably enlarged scale. A plurality of dot-like blackened portions A2 of the printing medium are shown, which are situated at the intersections of the printing row lines R1 to R5 with the printing column lines C1xe2x80x2 to C5xe2x80x2. It is apparent that the area of blank portions B2 is almost vanishingly small in comparison with the area of the blank portions B1 and that a subsequently continuous black area is obtained. Furthermore, this has the advantage that substantially the maximum attainable image contrast can be obtained, which provides a substantial improvement of the reproducibility of details of the contents in the case of copying of the contents of a document onto a printing medium.
The invention provides that the first conversion information and the second conversion information can be processed in the simplest possible manner.
The invention provides that the conversion information is directly available in the data conversion means and it is consequently not necessary to apply the conversion information to the data conversion means. Moreover, this has the advantage that the first conversion information and the second conversion information can be processed directly by the data conversion means without the use of data processing means external to the data conversion means.
The invention provides that the correct conversion information for the conversion of the scan data can be selected in accordance with the conversion mode of the data conversion means.
The invention provides that the selection of the first conversion information and the second conversion information is effected inside the data conversion means by the conversion information selection means, which are preferably included in the data conversion means.
The invention provides that production at minimal costs is guaranteed in the case of suitably large quantities.
The invention provides that in the case of a difference between the scanning row feed of the scanning means and the printing row feed of the thermal printing means the scan data can be converted into printing data that can be printed by the thermal printing means in the seconds print mode. Thus, in the case of a scanning row feed equal to 2 times the printing row feed the print data representing one row are supplied 2 times. Accordingly, in the opposite situation said data supply halved, i.e. the print data representing every seconds row are suppressed.
The invention further provides that in the case of dot-by-dot scanning of the document contents by scanning means operated in the second scan mode the document contents can be scanned in the feed direction of the document in such a manner the dots overlap. This has the additional advantage that a higher resolution can be achieved in the feed direction of the document although the scan dot size is maintained. This further yields the advantage that the document contents in the feed direction of the document can be scanned in a coherent manner, as a result of which the scan data thus generated represent the document contents with a high accuracy. This further yields the advantage that in the second mode of the scanning means an adjustment of the scanning row feed to the printing row feed in the seconds print mode of the thermal printing means which can be connected to the scanning device in accordance with the invention, as a result of which the document contents can be scanned with a resolution in the document feed direction equal to the resolution during printing in the second print mode of the thermal printing means.
The invention further provides that during dot-by-dot printing by means of the thermal printer in the second print mode of the thermal printing device in accordance with the invention, while the document is advanced by means of the printing medium feed means, printing can be effected in such a manner that the dots overlap in the feed direction of the printing medium, and that received scan data can be converted into print data by means of print data adaptation means included in the thermal printing device in accordance with the invention, which print data can be printed the thermal printing means set to the second print mode.
The invention will now be described in more detail with reference to the drawings, which show an embodiment given by way of example but to which the invention is not limited.